1991 Cadillac Seville Question: car loses power going up hills

Pull mass air flow sensor and clean with maf cleaner or electronic parts cleaner. Also, this sounds like a spark plug coil going bad the check engine light may be coming soon.

Does not have a mass airflow sensor. Just because you don't have a check engine light on doesn't mean you don't have a trouble code stored. Find a tech that can read OBD1 codes and serial data. Hopefully it will be someone who knows what they are seeing on the scanner.
You also need to perform a fuel pressure and volume test. I suspect you have a bad fuel pump. Make sure that you have this done with a fuel presure tester, not just pressing the schrader valve on the rail.